Dad's horror as he realises car has been stolen with two-year-old son in the back

A dad experienced a parent's worst nightmare after his car was stolen with his two-year-old son still inside.

Driving to the shops in Victoria, Australia with his young son snoozing in the back of his car, one dad ended up experiencing a terrifyingly nightmarish situation.

Parking up outside a shop to buy ice cream, he decided he'd allow the two-year-old to continue his peaceful slumber instead of waking him up.

Leaving the vehicle running so he could keep the air conditioning on, the dad never went more than 30 metres from the car as he stepped out for the snack and was away for only a minute.

However, that window of opportunity was enough for some nefarious bugger to get in and drive it away, taking the dad's young son along with the car.

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Police reckon the thief had been watching the car before deciding to steal it but failed to spot there was a child inside having a nap.

They soon realised their mistake pretty quickly as they stopped shortly after nicking the motor, putting the two-year-old by the side of the road before continuing their escape.

Detective Acting Senior Sergeant Grant Lewis said 'you'd hate to think what could have happened' if the thief hadn't realised for much longer that the two-year-old was in the car.

He said: "[He has] stolen that vehicle, driven about 350m through the rear of the Chelsea shops before he’s obviously realised there’s a child in the vehicle.

"He’s then stopped the car, put the child on the side of the road ... and driven off erratically southbound on Nepean Hwy towards Frankston."

"He remained where he was, but he was very distraught. A 30°C day with lots of cars and lots of traffic. You’d hate to think what could have happened."

The boy was rescued by members of the public who called the police after spotting him by the side of the busy road.

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Fortunately the boy wasn't injured, having not moved from his spot by the side of the road before people could get to him, but was said to be 'clearly traumatised and upset'.

It was also a 'horrifying' moment for his dad, Jake, who realised his car had been stolen with his son inside and was left pacing up and down the street in a panic as he tried to call for help.

Police said they would not be pursuing charges against Jake for leaving his son unattended in the car, saying it was 'serious' but that they 'don't want to victim shame or victim blame'.

Jake has urged other parents not to 'make the same mistake I did'.